The present invention relates to a non-ferrous metal smelting furnace used for smelting a non-ferrous metal such as aluminum and, more particularly, to a non-ferrous metal smelting furnace having a material preheating tower.
In recent years, a material is preheated and then used in smelting of a non-ferrous metal such as aluminum for the sake of energy saving. That is, a material preheating tower which also serves as a flue is provided to a smelting furnace, and a cold material in the heating tower is preheated by an exhaust gas which is already used in smelting. For example, in order to smelt a large amount of aluminum material, e.g., a scrap, a smelting furnace having a preheating tower as shown in FIG. 4 is used as an aluminum concentrated smelting furnace.
In FIG. 4, a reverberatory furnace type smelting furnace A constituted by refractory bricks includes a preheating tower B which is also constituted by refractory bricks at its upper side portion. The preheating tower B has a material charging port C and an exhaust port D at its upper portion and also serves as a material charging portion and a flue of the smelting furnace A. A lower portion of the preheating tower B constitutes a smelting chamber E, and a smelting burner F is provided at a side wall of the smelting chamber E. A molten metal retaining chamber G which causes the smelting chamber E to communicate with the lower portion includes a heat insulating burner H at its upper furnace body, and a molten metal discharging chamber J is provided adjacent to the molten metal retaining chamber G so as to communicate with the lower portion. Therefore, a material scrap charged from the material charging port C moves downward while being heated by an exhaust gas moving upward in the preheating tower B, and smelted by the smelting burner F at the smelting chamber E. The resultant molten metal is heat-insulated by the heat insulating burner H and retained in the molten metal retaining chamber G, and then discharged or pumped out from the molten metal discharging chamber J as needed.
In the smelting furnace A having the above arrangement, a material is smelted by a combustion flame of a high temperature of the smelting burner F in the smelting chamber, and an exhaust gas having its heat inertia is directly moved upward in the preheating tower B to preheat the material and then exhausted from the exhaust port D. However, upon smelting of the material, the material is smelted directly by a combustion flame of the smelting burner F, i.e., the material is smelted in an oxygen atmosphere. Therefore, when a material having a high oxidizing property and a wide surface area, such as an aluminum scrap, is used, an oxidizing rate is increased to significantly decrease the smelting yield of the material. In addition, since paths of an exhaust gas in the preheating tower B are not uniform, a specific portion is locally overheated to cause blow of a heating gas, resulting in a decrease in an effective heat transfer area of the material, significant heat energy loss such as a rapid decrease in heat recovery ratio, and an oxidation loss and evaporation loss of the metal caused by local overheating of the material, in the preheating tower B.